I think my ASUS router somehow "poisoned" my AT&T's fiber gateway...

[SolidSonicTH]

I don't want to sound like I don't know what I'm talking about but it's the only conclusion I can draw.

I put my AT&T fiber gateway into IP Passthrough mode so I could use my own router behind it. This worked for a long time but as of late (maybe the last month and a half) we keep getting dropped pages whenever we try to load certain sites (and it's very inconsistent, it seems like whatever was most recently cached into DNS is able to stay there but anything that's even slightly stale becomes inaccessible) and other Internet dropouts (like streaming from our smart TV). I tried a bunch of things (including separating devices onto just AT&T's wifi outside of the Ai Mesh network) and at this point all I've got is to completely disconnect my own hardware from the gateway and run purely on AT&T's internal network directly, which I absolutely despise for how little control it affords me but I need functional Internet.

I need some insight here because I feel like the only reasonable understanding I have in this situation is that my ASUS router (a ZenWifi AX) is corrupting the DNS requests the gateway is making somehow and thus trying to browse the web becomes a constant struggle (where I guess they want to send me in two different directions or something). I would think IP Passthrough would just delegate all routing and Internet DNS requests to the router behind the gateway but...I'm not sure why this is happening (especially when I can't recall this ever happening before). I had Cloudflare set up as the main DNS (1.1.1.1) for my router so...I dunno, does it not like that? Although even when I had devices outside of my own networking hardware they'd drop out at the same rate as stuff that was behind it too.

 

[Justinh]

Although even when I had devices outside of my own networking hardware they'd drop out at the same rate as stuff that was behind it too

You are saying a direct connection to the GW or going thru your router produce the same results? Then wouldn't that mean there is a problem with the GW or the connection to it?

 

[eibgrad]

I assume IP Passthrough is effectively placing the ISP router+modem into bridge mode.

You don't *have* to use bridge mode. It's just preferred, since it passes the public IP to your WAN, and you avoid a double NAT situation. But for most ppl and situations, a double NAT is not usually a problem. You just have to make sure the ISP's device and your router are using different private IP networks.

Should we assume all is well if you're configured for double NAT rather than IP Passthrough (bridged)?

 

[Justinh]

Passthrough is double-NAT; AT&T's fiber gateway does not have a true bridge mode.

 

[eibgrad]

Passthrough is double-NAT; AT&T's fiber gateway does not have a true bridge mode.

Then I assume it's just giving the "illusion" of a public IP on the router's WAN? If so, why bother if it's still double NAT'd?

 

[Justinh]

It is one of 3 simplified ways the GW gives to the user to get the WAN connection to the router, and the firewall is excepted for that device. This would make it easier for people to configure for those wanting/expecting bridged mode, I suppose.

 

[eibgrad]

It is one of 3 simplified ways the GW gives to the user to get the WAN connection to the router, and the firewall is excepted for that device. This would make it easier for people to configure for those wanting/expecting bridged mode, I suppose.

Thanks. I've never used such a thing, but based on what I'm hearing, I don't see the point, esp. if it's causing problems. Would be different if it was a true bridge, but otherwise, you're effectively in the same boat w/ a double NAT.

 

[Justinh]

Just to make sure I'm not misleading anyone @eibgrad , here is a trace from my PC (where my GW is in passthrough mode):
Tracing route to asus.com [103.10.4.227]
over a maximum of 30 hops:
1 <1 ms <1 ms <1 ms myrouter [192.168.10.1]
2 1 ms <1 ms <1 ms 192.168.1.254 <- this is the GW
3 2 ms 2 ms 2 ms 108-x-x-x.lightspeed.brhmal.sbcglobal.net [108.x.x.x]
4 5 ms 5 ms 4 ms 99.173.217.18

This is double-NAT, right?
This guy says that if you can't connect to the GW from behind the router then you are not double-NAT'd, but I can connect to the GW. The only diff is I'm using DHCPS-automatic instead of fixed. I'll have to try fixed to see if it makes a diff (don't know why it would).

 

[SolidSonicTH]

You are saying a direct connection to the GW or going thru your router produce the same results? Then wouldn't that mean there is a problem with the GW or the connection to it?

They produce the same results if the router stays connected to the gateway, even if I'm not connected to the router.

But removing the router entirely seems to have stopped the dropouts.

 

[Justinh]

Are you using DHCPS-automatic or fixed? Do you normally have other devices connected directly to the GW?
What WAN DNS service are you using?

 

[SolidSonicTH]

I had used both but usually just automatic.

No, just the router.

Cloudflare's 1.1.1.1 service.